Methods of using tires and scrap rubber in the manufacture and melting of steel and other metals

ABSTRACT

A method of using scrap rubber and other scrap materials, such as tires or parts or pieces of tires, to manufacture or melt steel and other metals in a furnace is disclosed. The scrap rubber may be used as a carbon source for the manufacture of steel and other metals, and may be used as an energy source to melt the scrap metal used to make the steel and other metals. The net benefit of this method includes reducing the amount of scrap rubber, such as tires, to be sent to a waste disposal facility or landfill, thereby improving the environment. In addition, by increasing the use of scrap rubber as a source of energy for steel or metal production, less energy is required from other sources.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/719,586, filed Mar. 8, 2010, now U.S. Pat. No. 7,883,566, which is acontinuation of U.S. application Ser. No. 12/489,837, filed Jun. 23,2009, now U.S. Pat. No. 7,674,317, which is a continuation of U.S.application Ser. No. 12/165,002, filed Jun. 30, 2008, now U.S. Pat. No.7,553,351, which is a continuation of U.S. application Ser. No.11/108,950, filed Apr. 19, 2005, now U.S. Pat. No. 7,393,379, whichclaims benefit to U.S. Provisional Application Ser. No. 60/563,701,filed Apr. 20, 2004, now abandoned.

FIELD OF THE INVENTION

The invention relates generally to the melting of scrap metal in afurnace using rubber tires, or parts of rubber tires, as an additionalenergy source. The invention also relates generally to the inclusion ofrubber tires, or parts of rubber tires, as a carbon component for themaking of steel and other metals.

BACKGROUND OF THE INVENTION

It is known to use scrap tires, or parts of tires, as a supplementalfuel source and carbon source for steel melting in an electric arcfurnace. The techniques and methods of such use are described in U.S.Pat. No. 5,322,544 and U.S. patent application Ser. No. 09/974,199, nowabandoned, both of which are in the name of Franklin Leroy Stebbing andboth of which are incorporated herein by reference in their entirety. Asdescribed in U.S. Pat. No. 5,322,544, recycling scrap tires into steelor using them as a heat source improves the environment by removing thetires from landfills where they do not degrade but do create a firehazard. Additionally, a single scrap tire, weighing about 20 pounds, hasabout the same heating value of coke, approximately 15,000 BTU's perpound, or approximately, 300,000 BTU's per tire. In the manufacture ofsteel, scrap tires, which are so plentiful that they have a near zerocost, can be used as a substitute to coal or coke as the heating source,thereby significantly reducing the costs to manufacture the steel. Asdescribed in U.S. patent application Ser. No. 09/974,199, the scraptires can be bundled with scrap steel in a charging bucket and then thecontents of the bucket placed in the furnace where the bundled tires andscrap steel are recycled into steel. The present invention describedherein builds upon the known techniques and methods of using scrap tiresor scrap rubber in the manufacture of steel, as set forth in U.S. Pat.No. 5,322,544 and U.S. patent application Ser. No. 09/974,199.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a system that permits the use of the manyforms of tires and scrap rubber in the furnace. The invention allows thetires to be inserted into the furnace at a more precise and controlledrate, time, and location. To this end, for example, by inserting thetires at a slower rate into the furnace and separate from the scrapsteel, as compared to batch feeding them or feeding them as tires andscrap steel bundles, it is possible to use larger quantities of tires ata specific controlled location and time. In an exemplary application,four tires or the equivalent of four tires may be added per ton of steelto be produced, as compared to two tires per ton ordinarily expected. Abenefit with the increase in the amount of tires that can be used is thedecrease in the number and amount of tires to be sent to a waste tiredisposal facility or landfill, thereby improving the environment, andputting more scrap tires to beneficial use. In addition, by increasingthe use of tires as a source of energy for steel or the metalproduction, less energy is required from other sources for such steel ormetal production.

The invention further allows the use of tires in many forms, so that thetires can be more readily handled and stored before they are put intothe furnace. Also, the present invention allows the tires to be put intothe furnace separate from the scrap metal that is also to be put intothe furnace. Unlike previous methods and techniques, the invention doesnot require the combining of the tires with the steel or scrap metalprior to the placement of the tires and scrap metal into the furnace. Byeliminating the tires from the charge bucket, more available space forthe scrap metal is created in the charge bucket. This can be especiallyvaluable in some melt shops where headroom or other factors limit chargebucket size. Also, it is no longer necessary to transport the chargingbuckets to a location where the tires are stored, as is the case in manyelectric arc furnace shops.

The invention also allows the tires to be injected into the furnace atvery elevated temperatures, thereby increasing the efficiency of thecombustion of the tires. Moreover, the invention allows the tires to beinjected into the furnace continuously and in a location mostadvantageous, such as while a foamy slag process is taking place. Thisallows the carbon monoxide that is being formed by the foamy slagprocess to convert to carbon dioxide with additional heat generationinside of the furnace—a result of the catalytic effect of the tires.With the invention, the tires may be placed or injected into the moltenmetal bath in the furnace so as to increase the carbon level in theliquid steel or metal to the desired level for the type and grade beingproduced.

Other features and advantages of the invention will become apparent tothose skilled in the art upon review of the following detaileddescription, claims and drawings in which like numerals are used todesignate like features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of exemplary techniques for insertingtires or parts of tires into a furnace for the manufacture of steel orother metals.

Before the embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of the components setforth in the following description or illustrated in the drawings. Theinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. Also, it is to be understood that thephraseology and terminology used herein are for the purpose ofdescription and should not be regarded as limiting. The use of“including” and “comprising” and variations thereof is meant toencompass the items listed thereafter and equivalents thereof as well asadditional items and equivalents thereof.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention is generally depicted in FIG. 1, but may be embodied invarious forms. As used herein, the term “tires” is to be broadlyinterpreted to include whole tires, tire pieces, parts, sections, bales,powder, particles, chunks, and the like. With the teachings andprinciples of the present invention, the term “tires” is also to beunderstood to encompass other types of rubber or rubber products, suchas waste hoses, scrap rubber materials, rubber pieces, parts, sections,powder, particles, chunks, and the like, or any other similar product ormaterial that is suitable for use as carbon or fuel in a steel or metalmaking furnace.

Referring to FIG. 1, the invention includes a furnace 10 that has anopening 12 positioned above or in the roof of the furnace 10 forinserting tires, or parts of tires. The furnace 10 may be an arc furnaceor any other furnace used for melting steel or metal. It should beunderstood that the invention is not limited to the type of furnace usedfor melting steel, that the teachings and principles of the inventionmay be applied to all types of furnaces that permit the use of tires aseither fuel or a carbon source.

To transport to and place the scrap steel or metal into the furnace 10,a number of devices and techniques are possible. The device might be aconventional charging bucket that is filled with scrap steel and ismoved to a location above the furnace where the contents can be emptiedinto the furnace. The device may include a conveyor that is used toconvey the scrap steel directly into the furnace in a continuous orsemi-continuous mode. A similar device includes a shaft that is filledwith scrap metal, and through gravity, the scrap metal moves toward andinto the furnace. Typically, the previously mentioned conveyor and shafthave a dual purpose. The conveyor or shaft is enclosed and thisenclosure is also used to provide a duct for the removal of the hotexhaust gases from the furnace operation. These hot gases come incontact with the steel or metal scrap to preheat the steel or metalscrap before it enters the furnace.

The aforementioned devices and techniques to transport and place thescrap steel or metal into the furnace 10 may also be used to transportand place the tires, or parts of tires, into the furnace 10 separatelyfrom the scrap steel or metal. That is, a conveyor may be used totransport and deposit the tires into the furnace 10, a charging bucketor box may be used to transport and charge the tires into the furnace,or a hopper may be located in proximity to the furnace 10 and used as afeeder to introduce the tires into the furnace 10.

Alternatively, the opening 12 in the furnace 10 roof or sidewall may beused to permit any size tire or tire bales or pieces of tires to beinserted or dropped into the furnace interior and at any desired timeand rate so as to maximize the benefits of the melting and refiningprocesses taking place within the furnace 10. The opening 12 can alsoinclude a chute to direct the tires into a desired position within thefurnace 10. When used with a conveyor fed furnace such as Consteel®, thetires can be dropped into the furnace and the heat from the tires willbe drawn through the Consteel® conveyor enclosure by the exhaust fans,thereby providing additional heat to the scrap metal on the conveyor.The tires can be added in a location opposite the conveyor opening tomaximize the travel distance from the point of deposit to the conveyorentrance thus maximizing residence time in the furnace for best heattransfer to the scrap in the furnace but also to allow the tiressufficient time to more fully combust before the heat is drawn into theConsteel® enclosure to preheat the scrap. When used with a shaft furnacesuch as that manufactured by Fuchs, the tires would likewise bedeposited to fully maximize the combustion and to gain contact time withthe scrap in the furnace. In some instances, it is advantageous tocombust the tires alone, prior to adding the scrap steel. This heatenergy is drawn through the scrap metal in the shaft or the feedingconveyor, thus preheating it before it is moved into the furnace proper.

As another exemplary alternative, a pneumatic powered gun 14 may be usedto put the tires into the furnace 10. In this embodiment, the tires arein a granulated or powdered form or suitable pieces and are blownthrough a tube or pipe 16 and into the furnace 10. The gun 14 can usecompressed air or other gases to propel the tires or tire pieces throughthe pipe 16. Alternatively, the gun 14 may simply be a tube forinserting the tires and tire pieces into the furnace 10. The gun couldbe used through the door to “cut in” scrap like a conventional carbonlance and also to provide the added benefit of CO conversion. In asimilar fashion, tire pieces can be used to augment or replace carbon inthe sidewall burners found in most electric arc furnaces to gain theadvantages accruing from the use of tires in place of coal.

The gun 14 can also function as a burner, with the tires or tire piecesserving as the fuel and using air and/or oxygen for combustion. In thisembodiment, the tires serve as an additional energy source for thefurnace 10. The air can be conveyed by the same pipe as the tires or bya separate pipe 18, as would likely be the case if oxygen were used topromote or enhance the combustion of the tires.

Yet another alternative device or technique for inserting the tires intothe furnace 10 includes the use of a thrower device to throw the desiredamount of tires into the opening 12 in the furnace 10, or through a dooror other suitable opening (not shown). The thrower device would be usedas an alternative to the gun in the situations where the tire pieceswere not suitable for gunning into the furnace because of the size orshape of the pieces, or if the tires contained wire or bead materialsfrom the tires that were interfering with the operation of the gun. Thethrower device may be configured to work in conjunction with thespecific size and configuration of tires being used. That is, thethrower device may be configured to accommodate any size tire orcombination of tire sizes, along with any size of tire particles, largeor small.

By adding the tires separately to the furnace 10, the conventionaltechnique of first combining the metal scrap and the tires, and thenputting the combined metal scrap and tires into the furnace iseliminated, thus saving time, effort, and resources. Moreover, thisallows the tires to be added separately and directly to the furnace 10in controlled quantities and at the correct time and location inside ofthe furnace to obtain maximum benefit. Also more space is created in thecharging buckets for additional scrap metal.

More particularly, the objective in operating the furnace is to addenergy at the maximum rate possible without causing damage to thefurnace, or wasting energy that cannot be absorbed by the scrap metalquickly enough. This is desirable because of the large energy lossesthat occur to the water cooled furnace walls and roof and also to thefurnace fume exhaust duct, combustion chamber, and dust collector. Thelonger the time taken to bring the scrap to tapping temperature, and/orholding at this temperature, the greater the heat losses. Because of theheat lost through radiation, equipment water cooling, and exhaust gases,the amount of total heat lost is proportional to the time spent inheating the scrap to molten temperature and holding at this temperaturebefore tapping. The higher the rate of heat input, the lower the heatlost to the surroundings because of the time factor. Through themodulated, controlled, insertion of tires to the furnace, separate fromthe scrap steel, the heat lost is better controlled.

Apart from the heat lost, the cost of energy is also a majorconsideration, with electricity the most expensive, followed by naturalgas, coke, coal and finally scrap tires, which have a negative cost(because they provide a disposal fee for consuming them along with somegain in the scrap steel which they contain). By replacing thetraditional heat sources, such as electricity, with scrap tires,significant cost savings can be achieved. More specifically, the cost ofelectricity is highest at the early stages of the melting cycle becausethis is the time when the maximum amount of energy can be transferred tothe scrap because it is cold and can accept heat more readily and alsobecause the electric arc is shielded by the scrap, reducing damage tothe furnace walls and roof. There is a power company “demand charge” forthis rapidly consumed electrical energy—a charge that is established bythe maximum rate of electrical power used during perhaps afifteen-minute period in perhaps a twelve-month cycle. Different powercompanies have differing schedules. With the technique of applying thetires to the furnace separately from the scrap steel, this is also thetime when the energy from the scrap tires can be used to reduce thedemand charges and replace all or part of the electrical energy consumedduring the initial and early stages of the melting cycle, while thescrap is still solid and relatively cold and able to accept the energyfrom the tire flames as it passes through the scrap. Thus, the use of amodulated, controlled, throttled flow of energy from the tires toreplace electricity, (as well as gas, coke or coal) can result insignificant cost savings.

Tire energy can be the major source of energy in the early stages of theheating cycle, with natural gas consumption then in a reduced rate andelectricity gradually increased as the cycle progress but at adiminished rate at the beginning stages of the heat to save on demandcharges. As the scrap metal is turned to molten metal the amount ofenergy that can be added to the metal bath from sources other thanelectricity is decreased because the liquid bath surface tends toreflect energy rather than absorb it. Also the bath is protected andcovered by the insulating effects of the foamy slag. The solid tireparts can be dropped into or added to the bath, however, increasingcarbon content or reacted with oxygen for additional energy in the bath.

The trend in this industry is to reduce electrical energy by adding morechemical energy in the form of natural gas burners and coal because itis cheaper. There are differences in the equipment being used and themelting practices followed, so the results vary from mill to mill. It isclear however, that low cost chemical energy is a very desirablecommodity. It should therefore be appreciated that scrap tires clearlysupply this need. The rate of energy added to the furnace byelectricity, natural gas or coal injection is controlled. The rate oftire energy input needs to be controlled for the same reasons. Thisfurther allows the rate of energy release to be reduced so that thetires are not burning at a less controlled rate and consumed before thesteel scrap can capture the available heat energy, as can occur if thetires are bundled with the scrap steel prior to insertion into thefurnace.

Also, in another aspect of the invention, with the use of tires separatefrom the scrap steel, the other forms of energy being applied to thefurnace may be reduced or regulated in a more precise and controlledmanner. As indicated above, these energy inputs are usually natural gasor fuel oil with combustion air or oxygen, electricity, coal or coke.These other energy inputs into the furnace can be more preciselyadjusted to correspond to the rate of tire energy input since the tireenergy can now be controlled at a desired rate, as opposed to the knowntechniques of batch feeding the tires with scrap steel. In thisinvention, the tire energy is the primary source with the other energiesfilling the gaps not taken care of by tire energy.

Because the tires enhance the conversion of carbon monoxide to carbondioxide, the tires can be injected into the furnace slag area in alocation where this conversion can be most beneficial. The slag havingbeen made from the addition of lime and/or other slag forming materialshaving the desired flux and foaming properties. The tire injectionlocation is chosen so that the carbon monoxide released from the foamyslag can be converted to carbon dioxide before it enters, or while it ismoving through the scrap metal. The carbon monoxide bubbles are formedin the slag by the use of a lance that injects carbon, usually coalparticles, along with oxygen gas, directly or indirectly into the slagwhich is floating on the molten steel puddle in the bottom of thefurnace vessel. The foamed slag is in contact with, and partiallyenvelopes and engulfs the steel scrap above it. The carbon monoxidebubbles continually burst and this gas flows through the scrap metal andfinally is exhausted out through an exhaust port, usually a hole thefurnace roof, often referred to as a “fourth hole.” A large percentageof the available energy in this gas is lost because it exits the furnaceas CO rather than converting to CO2. In one method of the invention, thetires or tire pieces would be added to the coal mix during, or prior to,injecting into the slag, or the tires may be added independently of thecoal mix. The added tires facilitate the conversion from CO to CO2. Theratio and timing may be adjusted to allow the slag to form CO and thenconvert to CO2 after the foam had done its job, releasing the conversionenergy while it was passing through the scrap metal, thus heating thescrap metal. In another method, the tire or tire pieces would beinjected at a location above the slag but low in the scrap layer sothere would be sufficient mixing time for the tire fume to react the COto CO2. While the tires or tire pieces are burning in the scrap metalzone in the furnace, the heat from this exothermic reaction has a chanceto contact and transfer to the scrap as it passes through it, therebyimproving the rate of melting of the scrap metal. In another method, thetires are used to replace substantially all of the coal for slagfoaming. Thus saving the cost of the coal and assisting the COconversion.

Similarly, the tires can be injected directly into the furnace whilesteel scrap is being fed by a shaft or conveyor system. The tires areburned in the furnace while the hot gases generated from the tire fireare withdrawn by the fume collection system. This hot exhaust is pulledthrough the enclosure surrounding the shaft or scrap conveyor, whichcauses it to be in close contact with the scrap metal. The hot gaseswill heat the metal as the gases move through the scrap in acounter-flow direction to the direction of travel for the scrap. Thisgreatly enhances the purpose and value for having shaft or conveyor fedfurnaces because the amount of available heat captured by them will bemuch greater. This also increases the efficiency of using tires becausethe contact time for the flames in these enclosures is even greaterbecause the tires are gradually placed in the furnace so as to burn at aslower, controlled rate, giving the scrap metal more time to absorb theheat. This also allows any remnants of the CO to CO2 conversion to takeplace in the shaft or conveyor enclosure before it escapes.

By using tires in forms other than whole tires some of the more valuablecomponents of the tires can be removed before the residue from the tiresis used for furnace feed. For example, crumb rubber particles have valueas raw material for other products. The crumb rubber and other materialscan be removed from the tires first, before the residue is used as acarbon, fuel and scrap metal source for steel or metal manufacturing,thus, increasing the value of the scrap tires and helping to convertthem from a waste material to valuable assets.

Also, when the rubber material is removed from the tires the remainingtire material has a higher scrap metal content, which can increase itsvalue as a charge material for the furnace. Additionally, having ahigher metal content can permit the tire pieces to be handled with ascrap-handling magnet—a device typically found in steel scrap handlingfacilities and melt shops.

Injecting rubber from the tires directly into a hot furnace, separatefrom the scrap steel or metal, allows the rubber to be exposed to, andachieve a very high temperature almost instantaneously. This allows therubber to be incinerated very rapidly with more complete combustiontaking place inside of the furnace.

As stated above, the tires can be injected or placed directly into themetal bath so that the carbon from the tire is added directly to themetal. The tires provide a source of carbon, replacing coal or coke. Thetires can be injected in controlled amounts so that the level of carbonin the bath can be more precisely adjusted according to the type orgrade of steel being produced. This provides a more exact carbon levelto be achieved in the finished product. The amount of tires that may beadded may vary depending on the level of carbon required for the steel.

In summary, with various aspects of the present invention, the knownstep of combining the tires together with the metal scrap beforeintroduction into the furnace is eliminated. The efficiency for the useof tires as an energy source is increased, since the energy is consumedgradually, instead of all at once with known batch-feeding techniques,and also the efficient use of the energy from the conversion of CO toCO2 is enhanced because the catalytic effect is not wasted in a rapidrelease from the furnace before it has time to act. A larger totalquantity of tires can be converted to a useful function, greatlyimproving the environment. Total emissions from the process are improvedon a more or less continuous basis. An emission “spike” is eliminatedbecause of the more uniform application of the catalytic effect of thescrap tires. Also, other forms of energy now used in the furnaces can bereduced and replaced by scrap tire energy. With the principles andteachings of the invention, the production of many types of metalproducts including various steel alloys, iron alloys and the like can beimproved.

The above described invention provides several advancements over the artin the use of tires, or parts of tires, as a fuel source for steel orother metal melting, and as a carbon component for the making of steelor other metals. First, the invention improves air emissions from steelmelting. Second, the invention provides a way to convert additionalwaste materials, i.e., scrap tires or tire parts, to a valuablecommodity. Third, the invention provides a method for increasing scraptire consumption by the steel industry. Fourth, the invention eliminatesthe step of combining the scrap rubber from tires, or tire parts, withscrap metal prior to placing the scrap rubber in the furnace. Fifth, theinvention provides a technique of injecting and placing the rubber intothe furnace so that the rubber can be put into the furnace in thedesired amounts, at the desired times, and in the best location. Sixth,the invention allows the use of the many forms of tires or scrap rubber,e.g., bales, pieces, crumbs, shredded pieces, and the like, as a feedfor the furnace. Seventh, the invention allows the reduction of“electrical demand” charges and other electrical consumption charges.Eighth, the invention enhances the scrap preheating aspects of shaft andconveyor fed furnaces, such as Consteel® by increasing the energy forpreheating as a result of burning the tires and/or increasing CO to CO2conversion in the furnace or in the shaft or conveyor. Finally, theinvention produces steel or other metals by injecting carbon directlyinto the liquid metal using scrap rubber as a carbon source for thesteel whether the liquid metal is in the furnace or afterward when inthe ladle. One skilled in the art will appreciate that the inventionprovides still other advancements over the art as it pertains to the useof tires, or parts of tires, as a fuel source for steel or other metalmelting, and as a carbon component for the making of steel or othermetals.

Variations and modifications of the foregoing are within the scope ofthe present invention. It should be understood that the inventiondisclosed and defined herein extends to all alternative combinations oftwo or more of the individual features mentioned or evident from thetext and/or drawings. All of these different combinations constitutevarious alternative aspects of the present invention. The embodimentsdescribed herein explain the best modes known for practicing theinvention and will enable others skilled in the art to utilize theinvention. The claims are to be construed to include alternativeembodiments to the extent permitted by the prior art.

Various features of the invention are set forth in the following claims.

What is claimed is:
 1. A method of manufacturing steel and other metalsor metal alloys in a furnace comprising the steps of: applying aquantity of metal into a furnace; applying energy to the quantity ofmetal to commence the melting of the metal, wherein the melting metalforms a slag; and applying a quantity of an energy source to the slag inthe furnace, wherein the quantity of an energy source does not includeadded metal, and wherein the quantity of an energy source is selectedfrom the group consisting of whole tires, tire pieces, tire parts, tiresections, tire bales, tire powder, tire particles, tire chunks, wastehoses, carbon-based rubber materials, rubber pieces, rubber parts,rubber sections, rubber powder, rubber particles, rubber chunks,carbon-based waste materials and carbon-based scrap materials.
 2. Themethod of claim 1 wherein the step of applying the quantity of metal isperformed prior to the step of applying the quantity of an energysource.
 3. The method of claim 1 further comprising the step of applyingcoal or coke to the furnace.
 4. The method of claim 3 wherein the coalor coke is mixed with the quantity of an energy source prior to beingapplied to the furnace.
 5. The method of claim 3 wherein the coal orcoke is applied to the slag in the furnace.
 6. A method of manufacturingsteel and other metals or metal alloys in a furnace comprising the stepsof: applying a quantity of metal and a quantity of a carbon-basedmaterial into a furnace; applying energy to the quantity of metal andcarbon-based material to commence the melting of the metal, wherein themelting metal forms a slag; and applying a quantity of an energy sourceto the slag in the furnace, wherein the quantity of an energy source isselected from the group consisting of whole tires, tire pieces, tireparts, tire sections, tire bales, tire powder, tire particles, tirechunks, waste hoses, carbon-based rubber materials, rubber pieces,rubber parts, rubber sections, rubber powder, rubber particles, rubberchunks, carbon-based waste materials and carbon-based scrap materials.7. The method of claim 6 wherein the step of applying the quantity ofmetal is performed prior to the step of applying the quantity of anenergy source.
 8. The method of claim 6 further comprising the step ofapplying coal or coke to the furnace.
 9. The method of claim 8 whereinthe coal or coke is mixed with the quantity of an energy source prior tobeing applied to the furnace.
 10. The method of claim 8 wherein the coalor coke is applied to the slag in the furnace.